Limit switch



Oct. 27, 1959 R. c. MCBROOM LIMIT SWITCH Filed Sept. 26, 1958 INVENTOR.R ulnar]; C.ME1ruum BY a J ,p flzwammm United States Patent Q LIMITswrrcn Robert C. McBroom, Lynn, Mass., assignor, by mesne assignments,to the United States of America as represented by the Secretary of theArmy Application September 26, 1958, Serial No. 763,762

4 Claims. (Cl. 200153) This invention relates to a limit switch and moreparticularly a limit switch used to provide a take-off indication for aguided missile.

For launching a guided missile from a ground plat form it is necessaryto provide an electric signal to indicate the exact time of take-ofi ofthe missile from the launcher. The signal is provided by a limit typetake ofi switch mounted on the ground platform with the actuator of theswitch contacting the base of the missile. While the missile remains onthe platform, the actuator is held in a depressed position to hold theswitch open. As the missile rises the actuator is released to allow theswitch to close. While the missile remains on the platform it isnecessary to run complete electrical system tests and one of the testsnecessary is to ascertain that the take-oft switch is functioning. Meansare, therefore, provided to operate the switch to close same for testpurposes while the missile is in firing position.

An object of the invention is to provide a limit switch for guidedmissile launching provided with means to test the switch before firing.

A further object of the invention is to provide a spring biased limitswitch held in open position by a missile on a launching platform andmeans to move the switch before the missile is launched to check theoperation thereof.

Yet another object is to mount a limit switch on a pivoted plate so thatthe switch may be swung clear of the switch operator.

In the drawing:

Figure 1 is a plan view of the limit switch of the invention and beingpartly broken away to show the interior mechanism, and

Figure 2 is a cross-sectional view of the limit switch taken on the line2--2 of Figure 1.

Referring to the drawing the line A represents one side of a track orway on a guided missile launching platform. The missile when inlaunching position would be disposed above the line A in Figure l andwould be launched to the right or left.

The limit switch which forms the subject matter of this invention isindicated in its entirety by reference character 1 and may be rigidlyattached to the launching platform in any suitable manner. The casing ofthe switch is indicated at 2 and is provided with a cover plate 3attached thereto by means of bolts 4. Between the cover plate and casingis provided a sealing member 5 to provide weather-tightness for theswitch.

The switch casing is provided with opposite end walls 6 and 7 and theseend walls are provided with aligned apertures 8 and 9 for the receptionof operator pin 10. The pin 10 carries at one end an adjustable head 11adapted to contact a missile held in position for firing and at theother end a nut 12 to limit upward movement of the pin with respect tothe casing. Intermediate its ends the actuator pin is provided with ashoulder 13 and a spring 14 surrounds the pin and reacts between thecasing and shoulder to bias the pin in an upward direc- Fee tion. Thepin is further provided with a cam surface 15 and cylindrical portion28, the function of which will presently appear.

Mounted within the switch casing is a bolt 16 to which is pivoted'aplate 17 having an arcuate slot in the upper portion thereof. Alsomounted within the casing is a bolt or stud 19 which extends through theslot in the plate to limit the pivoting movement of the plate. The plate17 also carries an upstanding apertured flange 20. The lower wall 7 ofthe casing is provided with a second aperture 21 for the reception oftest actuator pin 22 which is connected to flange 20 at one end and hasa hand manipulable knob 23 at its other end disposed outside of theswitch casing. A coil spring 24 is disposed between the casing andflange 20 to bias the pivoted plate 17 to the right to the extentpermitted by slot 18.

The plate 17 has rigidly mounted thereon the box 25 which carries thecontact elements of the switch (not shown). The contact elements areoperated by operator button 26 which is biased to the right in Figure 1by means of spring 27 to close the contacts and which may be moved tothe left by cam surface 15 on pin 10 to open the contacts.

In operation a missile is placed in the launching way and the pin 10 isdepressed thereby such that the cam 15 actuates the operator button 26to open the switch contacts. The long cylindrical portion 28 of the pinpermits overtravel and allows for different positions of the mis sile onthe launching platform while still. operating the limit switch. When themissile is launched the pin 10 will be forced upwardly by spring 14 thusallowing the.

switch is for an operator to grasp knob 23 and pull downwardly. Thispivots the entire plate 17 about bolt 16 away from the pin 10 and allowsthe spring 27 to move the button 26 to the right to close the switchcontacts. When the operator releases the knob 23 the spring 24 willreturn the plate to the right and the button into contact with pin 10 toopen the switch contacts. Thus, the switch contacts cannot beaccidentally left closed after test with the missile in position forlaunching.

It will be apparent that the embodiment shown is only exemplary and thatvarious modifications can be made in construction and arrangement withinthe scope of the invention as defined by the appended claims.

I claim:

1. A limit switch comprising a casing, a contact carrying platepivotally mounted in said casing and having an operator button, biasingmeans to urge said operator button in one direction, an operatorslidably mounted in said casing adjacent said button and adapted toactuate said button against the action of said biasing means, a testactuator connected to said plate and being hand manipulable to swingsaid plate and operator button away from said operator to allow saidoperator button to move to the biased position regardless of theposition of said operator.

2. A limit switch adapted to be mounted on a missile launching devicecomprising a casing, an operator slidably mounted in and extendingexteriorly of said casing, a spring surrounding and urging said operatorin an outward direction, said operator being adapted to be depressedagainst the action of said spring by a missile in position forlaunching, an operator button mounted in said casing and biased intocontact with said operator and means to move said operator button out ofcontact with saidoperator to -permit test of said switch while themissile is in position. 7

3. A limit switch comprising a casing having opposed end walls withaligned apertures therein, a plate pivoted in said .casing and having acontact operating-button mounted thereon,-a spring biasing saidoperating button outwardly of said plate, an operator slidable in thealigned aperturesof said casing and being spring biased in onedirection, a cam surface onsaid operator adapted to depress saidoperatingbutton when said operator is moved against its spring bias, atest actuator connected to said plate and operable to swing said plateand operating button clear of said operator-and a spring surroundingsaid test actuator and reacting between said plate and casing to urgesaid operating button'into contact with said operator.

'4. A limit switch comprising a casing having end and.

' side walls, said casing having aligned apertures in the opposed endwalls thereof and a third aperture in one of said walls, a pivot pinmounted within said casing, a plate in said casing pivoted on said pivotpin and having a contact operating button thereon, a spring biasing saidoperating button outwardly of said plate, an operator slidable in thealigned apertures of said casing and being spring biased in onedirection, a cam surface on said operator adapted to depress saidoperating button when said operator is moved against said spring bias, atest actuator connected to said. plate. and extending exteriorly of saidcasing through said third aperture, said test actuator being manuallymanipulable to swing said plate References Cited in the file of thispatent UNITED STATES PATENTS Crew Sept. 12, 1944 Framhein Apr.;13,.'1954

